Intake system of outboard motor

Abstract

An intake system of an outboard motor including a vertically arranged V-type engine comprises, an intake manifold connected to the intake ports, a surge tank connected to the intake manifold and disposed at a rear side from a central portion of the engine, a throttle body provided with a throttle valve, a plurality of intake passages for high revolution operation of the engine. The intake passages for high revolution operation extend from the surge tank and are communicated with the intake manifold, and the intake passages for low/intermediate revolution operation extend from the surge tank and are joined with the intake passages for high revolution operation, respectively. Each of the intake passages for low/intermediate revolution operation has a length longer than that for high revolution operation. A valve open/close mechanism is also disposed for opening/closing all at once portions upstream side of the joined portions of both the intake passages of the engine.

What is claimed is:  
     
       1. An intake system of an outboard motor, which includes a vertically arranged V-type engine covered by an engine cover and having a crankshaft extending perpendicularly therein and right and left cylinder banks opened in V-shape towards a rear side as viewed in a plan view, and in which intake ports of respective cylinders are opened to the inside of the V-shape arrangement, said intake system comprising: 
       an intake manifold connected to the intake ports;  
       a surge tank connected to the intake manifold and disposed at a rear side from a central portion of the engine;  
       a throttle body mounted to the surge tank and provided with a throttle valve;  
       a plurality of intake passages for high revolution operation of the engine, said intake passages for high revolution operation extending from the surge tank and being communicated with the intake manifold, said plural intake passages for high revolution operation having a number corresponding to a number of the cylinders of the engine;  
       a plurality of intake passages for low/intermediate revolution operation of the engine, said intake passages for low/intermediate revolution operation extending from the surge tank and being joined with said intake passages for high revolution operation, respectively, said plural intake passages for low/intermediate revolution operation having a number corresponding to a number of the cylinders of the engine and each of said intake passages for low/intermediate revolution operation having a length longer than that for high revolution operation; and  
       a valve open/close mechanism disposed for opening/closing, all at once, portions upstream side of the joined portions of the intake passages for low/intermediate revolution operation and the intake passages for high revolution operation,  
       said intake passages for low/intermediate revolution operation extending, as viewed in a plan view, from both side surfaces of the surge tank towards both outsides in a width direction of an outboard motor body so as to be positioned at a rear portion of both the cylinder banks of the V-type engine, so that the surge tank protrudes over the intake passages for low/intermediate revolution operation towards a rear side of the V-type engine, and said intake passages for low/intermediate revolution operation having inlets on the side of the surge tank which are opened in vicinity of inlets of the intake passages for high revolution operation.  
     
     
       2. An intake system of an outboard motor according to  claim 1 , wherein said plural intake passages for low/intermediate revolution operation includes a half for left-side cylinder bank of the V-type engine to a right side of the surge tank and another half for right-side cylinder bank of the V-type engine to a left side of the surge tank so that axial directions of the intake passages for low/intermediate revolution operation at the joining portions thereof to the intake passages for high revolution operation are substantially coincident with axial directions of the passages of the intake manifold. 
     
     
       3. An intake system of an outboard motor according to  claim 1 , wherein each of said intake passages for low/intermediate revolution operation once extends towards an outside direction from a width direction of the outboard motor body, then is turned in U-shape in a vertical direction and extends again towards an inside direction in the width direction to thereby join the intake passages for low/intermediate revolution operation of the engine to the intake passages for high revolution operation of the engine. 
     
     
       4. An intake system of an outboard motor according to  claim 1 , wherein said intake passages for high revolution operation of the engine are provided with surge tank side inlets arranged in a vertical single line in parallel to the crankshaft of the engine, said valve open/close mechanism includes a plurality of butterfly valves disposed at the surge tank side inlets, and said butterfly valves are provided with a single valve rotating shaft having an axis substantially in parallel to the crankshaft of the engine and driven thereby. 
     
     
       5. An intake system of an outboard motor according to  claim 1 , wherein said valve open/close mechanism includes a plurality of butterfly valves disposed at surge tank side inlets of the intake passages for high revolution operation, an actuator, as driving means, mounted to a lower end of a valve rotating shaft extending from the lower surface of the surge tank, and an expansion rod extending from the actuator connected to a crankshaft connected to the valve rotating shaft. 
     
     
       6. An intake system of an outboard motor according to  claim 1 , wherein said throttle valve is provided on one end of said surge tank and said valve open/close mechanism includes a drive member provided on another end of the surge tank. 
     
     
       7. An intake system of an outboard motor according  claim 1 , wherein said V-type engine is a water-cooled 6-cylinder V-type engine, three in each side of V-arrangement. 
     
     
       8. An intake system of an outboard motor according to  claim 1 , wherein said surge tank includes a lid member. 
     
     
       9. An intake system of an outboard motor according to  claim 1 , wherein said surge tank, said intake passages for high revolution operation of an engine and said intake passages for low/intermediate revolution operation of the engine are divided into front and rear halves from a division surface along an extending direction of the intake passages for low/intermediate revolution operation.